Re: hardware channel mixing [EMU10K1 DMA]

[Lee Revell <rlrevell@joe-job.com>]

On Tue, 2004-09-07 at 15:16, Jaroslav Kysela wrote:
> On Tue, 7 Sep 2004, Lee Revell wrote:
> 
> > On Tue, 2004-09-07 at 04:23, Jaroslav Kysela wrote:
> > > On Tue, 7 Sep 2004, Lee Revell wrote:
> > > 
> > > > The interval timer seems to be intended exactly for this use; I am a bit
> > > > baffled as to why was the channel loop interrupt, a relatively obscure
> > > > feature, was chosen as the playback interrupt source.
> > > 
> > > No, in this case you don't get exact interrupt at period boundary.
> > > It seems bigger problem (wrapping) than having an extra voice.
> > > 
> > 
> > Hmm.  If this is the case then it really seems like the OSS driver
> > should not work at all then.
> 
> It works, but with higher latencies than application requested. You can 
> probably write a timer scheduler code, but it will be probably 
> a maintenance nightmare.
> 

Hmm, OK.  Guess I will have to try it.

> > You mentioned previously that removing the extra voice would only allow
> > 2 periods per buffer.  Do you mean that the interval timer could be used
> 
> Yes, if we can do proper interrupt in the middle of voice's buffer.
> 

OK.

> > How did you figure out the use of the channel loop interrupt, as this is
> > not used in the OSS driver at all?
> 
> I don't remember exactly. Maybe from old EMU8000 (because some things are 
> common) and the header file from OSS driver.
> 

Hmm, I will have a look at that one.

> > like I can implement the kX ASIO functionality without needing the extra
> > voice because the efx capture device provides a very high resolution
> > timer.
> 
> You can create a special playback PCM which will share efx interrupt, of
> course. But I don't know, how you expect to synchronize multiple streams
> for exact sample resolution, because you cannot start multiple playback
> streams using one i/o transaction for emu10k? chips.
> 

I think you can start a stereo stream using one I/O transaction, but
right, I think you are limited to opening 2 at a time.  Anyway it works
great in Windows with the kX driver so there must be a way.  If I have
to I will reverse engineer it.  Thanks for the info.

Lee



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